Long-term Stability of Endocardial Left Ventricular Pacing Leads Placed via the Coronary Sinus

Background: Left ventricular endocardial pacing leads placed via the coronary sinus (CS) are increasingly implanted to achieve cardiac resynchronization therapy (CRT); however, the long-term stability of these leads is unknown. We sought to determine the implant success and long-term stability of CS leads in our single center experience.
Methods: All consecutive patients who underwent CRT via implantation of the CS lead between January 1999 and December 2005 were included. Pacing thresholds at implant and during long-term follow-up were reviewed and the rate of acute (within 24 hours of implant) and chronic (>24 hours) lead failure was determined.
Results: A total of 512 patients (mean age 68 ± 12 years; 409 [80%] male) underwent CRT device implantation and were included. The CS lead implantation was successful on the initial implantation in 487 patients (95%) and subsequently successful in six patients (24%) in whom initial attempts were unsuccessful. Acute lead failure occurred in 25 patients (5.1%) and was most commonly due to persistent extra-cardiac stimulation. The rate of chronic lead failure was 4% in the first year and remained stable during long-term follow-up. The CS lead pacing thresholds remained stable with only minimal increase (1.42 ± 0.85 V/0.42 ± 0.25 ms vs 1.51 ± 1.05 V/0.47 ± 0.29 ms; P = 0.04).
Conclusions: Placement of a left ventricular pacing lead via the CS is feasible and safe in the vast majority of patients. Once placed, the CS leads remain stable with excellent pacing thresholds over the longer term.     

Effective long-term left atrial pacing using regular screw-in leads implanted within the coronary sinus

Passive-fixation leads positioned inside the coronary sinus (CS) have been found to be effective in LA pacing and sensing, but their use is limited by a high incidence of early and late dislodgment. Since anatomic studies have shown that the proximal part of the CS is surrounded by a relatively thick musculature, the feasibility, safety, and efficacy of acute and chronic coronary sinus pacing via regular screw-in leads positioned within the first centimeters of the CS were evaluated as compared to passive-fixation leads. Thirty-three patients (21 men, age 62 +/- 10 years) underwent dual chamber pacemaker implantation with LA pacing obtained via passive-fixation leads (7 patients) or regular screw-in leads (26 patients). The former approach was prematurely abandoned because of a high rate of acute and late lead dislodgment (42%). The chronic pacing threshold was 1.7 +/- 1.0 V at 0.67-ms pulse width and 1.47 +/- 1.3 V at 0.5-ms pulse width for passive- and active-fixation leads, respectively. In the CS active-fixation lead group, no postoperative pericardial effusion, CS lead dislodgment, nor diaphragmatic stimulation were observed. In this last group, steroid eluting leads (14 patients) have a statistically lower pacing threshold than noneluting steroid leads (12 patients) (0.88 +/- 0.23 vs 2.29 +/- 1.68 V, P = 0.011) at long-term follow-up. The use of regular screw-in leads implanted within the CS allows effective and safe long-term LA pacing without risk of dislodgment.     

Nonuniformity of AH Intervals During Stimulation at Different Left Atrial Sites

Studies in humans have found left atrial stimulation via the coronary sinus (CS) to elicit significantly shorter atrium-His (AH) intervals as compared to right atrial stimulation, but whether pacing at dijferent left atrial sites (anterior vs posterior left atrium, i.e., far distal vs proximal CSJ affects the AH interval has not been studied. Hence, in 22 patients, we compared the effects of stimulation from various atriai sites, including anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS, on; stimulus-atrium (SA), AH, and stimuIus-His intervals on the His bundle electrogram. Paced cycle length differed for each patient (range 900–350 msec, mean 532 ± 140 msec), but conduction intervals from different atrial sites were compared using identical cycle length in each patient. The mean SA intervals were 34 ± 10 msec, 57 ± 10 msec, 44 ± 11 msec, and 32 ± 8 msec with stimulation, respectively, from HRA, distal CS, mid-CS. and proximal CS (each significantly different except for HRA vs proximal CSJ. The mean AH intervals were 123 ± 23 msec, 104 ± 28 msec, 95 ± 15 msec, and 90 ± 18 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for mid-CS vs proximal CSJ. In 13 patients, the discrepancy in AH intervals during distal versus proximal CS stimulation was > 15 msec; in 9 patients this difference was only < 10 msec, considered within the range of measurement error. Thus, in a significant portion of patients, discrepant AH intervals were demonstrated during stimulation from the distal versus proximal CS. These previously undescribed observations suggest that electrophysiological studies on atrioventricular nodal conduction that involve left atrial stimulation must take into account actual location of the stimulation site (anterior or posterior) in order to properly interpret the findings.     

Backup Right Ventricular Pacing with a 0.035" Guidewire during Implantation of Left Ventricular Leads

Introduction: During implantation of biventricular devices, manipulation of the guiding sheath during localization of the coronary sinus (CS) ostium may result in injury to the right bundle and complete heart block. A preventive measure is to implant the right ventricular (RV) lead first, though this may interfere with manipulation of the guiding sheath and dislodge the permanent lead . We tested the feasibility of backup pacing with a 0.035" guidewire, advanced through the guiding sheath during CS localization.
Methods: One hundred six consecutive patients (mean age = 70 ± 11 years, 81 men) undergoing biventricular device implantation were studied. A 0.035" guidewire with an uncoated tip was advanced into the right ventricle through the guiding sheath, and unipolar capture threshold, R-wave sensing amplitude, and pacing impedance were measured.
Results: RV pacing was successful in all patients. The mean capture threshold was 3.8 ± 2.1 V/0.5 ms, R-wave amplitude 5.4 ± 4.3 mV, and pacing impedance 226 ± 78 Ω. No arrhythmia was observed during the tests. Two patients developed complete heart block during the implant procedure and were successfully paced temporarily using the 0.035" guidewire.
Conclusion: Temporary RV pacing, using a 0.035" guidewire within the guiding sheath, is a simple, reliable, and safe method that allows backup pacing in case of traumatic complete heart block, developing during the implantation of biventricular devices.     

Left atrial vein pacing: a technique of biatrial pacing for the prevention of atrial fibrillation

Biatrial pacing is a promising new therapy for drug refractory AF. This article reports two studies. First, an initial 14-patient experience with a novel technique for biatrial pacing. The authors attempted to pace from the LA vein branches of the proximal CS for LA stimulation. LA vein pacing would potentially offer the advantages of greater interatrial synchronization and possibly greater reduction in AF burden and also of lesser far-field R wave sensing and greater lead stability. Second, a postmortem series examining the number, size, and site of LA veins draining into the proximal CS is described. LA vein pacing was successful in 9 of 14 patients. LA vein electrode parameters have been stable during a median follow-up of 580 days. There were three early lead dislodgments but no other complications. In the second study, a postmortem analysis of 43 human hearts was performed. The study found that 38 (88.4%) of 43 hearts had at least one LA vein draining into the proximal 5 cm of the CS. In addition, 81.2% (33/43) had at least one vein greater than 4 Fr caliber. Thus, pacing in a greater proportion of patients might be achieved by the development and use of smaller (3, 4, and 5 Fr) electrodes. Furthermore, these smaller leads would obviously allow deeper advancement into the LA veins with the potential advantages of greater interatrial synchronization and lead stability and lesser far-field R wave sensing.     

Permanent Left Ventricular Pacing With Transvenous Leads Inserted Into The Coronary Veins

This paper describes a preliminary experiment - conducted jointly by 2 centers - of permanent left ventricular pacing using leads inserted by the transvenous route and through the coronary sinus into the cardiac veins of the left ventricle free wall. The aim was to obtain permanent biventricular pacing in a totally endocavitary configuration in pattents with severe LV dysfunction and drug-refractory heart failure. Two types of leads were used: nonspecific unipolar leads at the beginning of the experiment, followed by leads specifically designed to be used in the coronary sinus in a second step. The electrode could be fitted in an adequate location in 35 of the 47 patients (75.4%), with a 1.15±0.7 V acute pactng threshold and 11.8±5.7 mV R wave amplitude. The success rate was significantly higher with the specific electrodes (81.8% vs 53,3%, p < 0.001). The pacing and sensing thresholds upon implantation were not influenced by the type of lead or by the localization of the cardiac vein that was catheterized (great cardiac vein, lateral vein, postero-lateral or posterior vein, mid cardiac vein). In contrast, the pacing threshold was significantly lower (0.8 ± 0.2 vs L8 ± 0.8 V; p = 0.002) and the R wave amplitude tended to be greater (13.1 ± 4.5 mV vs 9.3 ± 6.5 mV; p = 0.07) when the tip electrode could be inserted distally into the vein, by comparison with a proximal site near the ostium. At the end of follow-up (10.2 ± 8.7 months), 34 out of the 35 leads were still fully functional, with a chronic pacing threshold of 1.8 ± 0.7 V and a R wave amplitude of 10.7 ± 6 mV. To conclude, permanent LV pacing via the transvenous route is possible in most patients, with excellent safety and long-term results.     

Single Pass Lead VDD Pacing in Children and Adolescents

Implantation of permanent pacemakers in children and adolescents is possible but usually is limited to single chamber generators. The natural growth of these patients may require physiological pacing, but until recently two leads were required for this type of pacing. The single pass lead VDD pacing mode makes posible physiological pacing by using only one lead, for both atrial sensing and ventricular sensing and pacing. The feasibility of VDD pacing using endocardial lead was evaluated in 16 children and adolescents with congenital or postsurgical atrioventricular block. Their mean age was 7.9 ± 4.9 years (range 1-16 years) and the smallest patient's weight was 8.2 kg. In all the patients, a single pass pacing lead with atrial sensing rings and bipolar ventricular pacing and sensing capability was implanted through the left or right subclavian vein. The pacemaker generator was implanted in a rectopectoral position. The mean atrial electrogram during the implantation was 4.2 ± 2.1 mV and 2.6 ± 1.9 mV after a mean of 1 week. The ventricular pacing threshold was 0.5 ± 0.2 V; the ventricular pacing impedance was 560 ± 95 Ω and the ventricular electrogram amplitude was 9.9 ± 2.1 mV. This is a first report to demonstrate the feasibility of atrial synchronous ventricular endocardial pacing using a single pass lead in a relatively large group of children and adolescents.     

The Effect of Radiofrequency Catheter Ablation on Permanent Pacemakers: An Experimental Study

Radiofrequency current is being investigated as an alternative to direct current shock for transcatheter ablation of cardiac arrhythmias. Permanent pacemakers are known to be susceptible to high frequency electromagnetic interference. This study was performed to examine the effects of transcatheter radiofrequency ablation on permanent pacemakers in a worst-case scenario. Nineteen pulse generators representing 16 models from seven manufacturers were acutely implanted in 12 dogs to assess their function during and after ablation. Pulse generators were implanted subcutaneously in the neck and connected to a transvenous permanent pacing lead positioned in the right ventricular apex. A 6F quadripolar electrode catheter was positioned approximately 1 cm from the tip of the permanent pacing lead. Radiofrequency current from an electrosurgical unit was applied between the distal electrode of the catheter and a large diameter skin electrode placed below the left scapula. Three additional ablation sessions were performed with the catheter situated 4-5 cm from the permanent pacing lead. Each ablation consisted of 15 W of radiofrequency power, delivered for up to 30 seconds. Twelve pulse generators were falsely inhibited during radiofrequency ablation while programmed to the VVI or DDD mode, nine of which continued to be inhibited while programmed to the VOO or DOO mode. Five pulse generators paced at abnormal rates, including three examples of one pulse generator model that displayed pacemaker runaway. Runaway was observed during eight ablations, resulting in two episodes of ventricular fibrillation. Eleven pulse generators reverted to noise mode behavior during ablation. Only three pulse generators were unaffected during ablation. No reprogramming or pacing system malfunctions were observed after cessation of radiofrequency current application or during ablations greater than 4 cm from the permanent lead.(ABSTRACT TRUNCATED AT 250 WORDS)     

Atrial Electromechanical Sequence and Contraction Synchrony during Single- and Multisite Atrial Pacing in Patients with Brady-Tachycardia Syndrome

Objectives: Investigation of which atrial pacing modality provides atrial synchrony and the most physiological atrial contraction pattern in patients with brady-tachycardia syndrome.
Methods: Fifteen healthy subjects and 57 patients with sinus node dysfunction, atrial fibrillation recurrences, and prolonged P-wave on the electrocardiogram treated with multisite atrial (MSA) pacing were studied. One atrial lead was implanted in the coronary sinus (CS) ostium area, the other at the right atrial appendage (RAA): RAA+CS group (28 patients), or Bachmann's bundle (BB) region: BB+CS group (29). Sinus rhythm (SR) and CS, RAA, BB, RAA+CS, and BB+CS pacing modalities were evaluated. Electromechanical delay (EMD) in atrial walls was assessed by tissue Doppler echocardiography. Interatrial (ΔinterA), intra-right (ΔRA), and intra-left (ΔLA) atrial dyssynchrony were calculated.
Results: During SR, in the study group versus controls, important ΔinterA: 55 ± 23 versus 22 ± 11 ms (P < 0.01) and ΔLA: 47 ± 21 versus 21 ± 6 ms (P < 0.001) were present. Single-site BB and both MSA pacing modes restored ΔinterA and ΔLA (ΔinterA: 24 ± 16, 20 ± 13 and 14 ± 9 ms, ΔLA: 28 ± 18, 28 ± 13 and 20 ± 10 ms during BB, RAA+CS and BB+CS pacing, respectively). CS pacing prolonged lateral RA EMD, while RAA pacing LA walls EMD, which resulted in ΔinterA persistence. CS pacing induced ΔRA (50 ± 23 vs 16 ± 8 ms, P < 0.0001 vs controls). Atrial contraction sequence during BB pacing resembled that observed in controls.
Conclusions: (1) Single-site BB and both MSA pacing modes restored atrial synchrony. (2) Single-site RAA and CS ostium pacing retained interatrial dyssynchrony; moreover, CS pacing created RA dyssynchrony. (3) Single-site BB pacing provided physiological atrial contraction sequence.     

Feasibility Of Temporary Biventricular Pacing In Patients With Reduced Left Ventricular Function After Coronary Artery Bypass Grafting

Background and Methods: Biventricular pacing improves hemodynamics after weaning from cardiopulmonary bypass in patients with severely reduced left ventricular (LV) function undergoing coronary artery bypass grafting (CABG). We examined the feasibility of temporary biventricular pacing for 96 hours postoperatively. Unipolar epicardial wires were placed on the roof of the right atrium (RA), the right ventricular (RV) outflow tract, and the LV free lateral wall and connected to an external pacing device in 51 patients (mean LV ejection fraction 35 ± 4%). Pacing and sensing thresholds, lead survival and incidence of pacemaker dysfunction were determined.
Results: Atrial and RV pacing thresholds increased significantly by the 4th postoperative day, from 1.6 ± 0.2 to 2.5 ± 0.3 V at 0.5 ms (P = 0.03) at the RA, 1.4 ± 0.3 V to 2.7 ± 0.4 mV (P = 0.01) at the RV, and 1.9 ± 0.6 V to 2.9 ± 0.7 mV (P = 0.3) at the LV, while sensing thresholds decreased from 2.0 ± 0.2 to 1.7 ± 0.2 mV (P = 0.18) at the RA, 7.2 ± 0.8 to 5.1 ± 0.7 mV (P = 0.05) at the RV, and 9.4 ± 1.3 to 5.5 ± 1.1 mV (P = 0.02) at the LV. The cumulative overall incidence of lead failure was 24% by the 4th postoperative day, and was similar at the RV and LV. We observed no ventricular proarrhythmia due to pacing or temporary pacemaker malfunction.
Conclusions: Biventricular pacing after CABG using a standard external pacing system was feasible and safe.